1. Field of the Invention
The present invention relates to a developing unit. More specifically, the present invention relates to a developing unit to which toner is supplied from a separate unit.
2. Background Information
Some developing units of image forming devices are constructed such that a fixed amount of toner is charged into the developing unit. The developing units are replaced when the toner runs out, which economically, is not preferable. On the other hand, if the amount of toner filled inside the developing units is increased, it will be difficult to miniaturize the developing unit.
In order to miniaturize the developing unit, the idea of having toner supplied from a separate unit has been proposed, as disclosed in Japan Unexamined Patent Publication No. 2001-134045. In the rotary developing system disclosed therein, a plurality of developing units are held in a rotary frame. A joint connects the toner supply device to the rotary developing unit. The toner supply device and the joint slide to open a shutter mechanism, allowing the joint to connect to a sub rotary developing unit stopped at a determined position.
In a conventional developing unit where toner is supplied from a separate unit, the joint mechanism, which connects the rotary portion in the rotary frame with a toner supply portion of the main body, and the shutter mechanism are required. However, the structure of the joint and the shutter mechanisms is too complex. In addition, since the sliding mechanism of the joint is required in addition to the rotary frame, miniaturization of the developing unit is possible only to a certain extent. Another invention disclosed in Japan Unexamined Patent Publication No. 10-198149 proposes the use of a pipe to supply toner instead. However, the tip of the toner supply pipe is open at all times, and no shutter mechanism is provided at the developing unit end. A problem in which the toner might splash out while supplying toner is not being considered.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved developing unit. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.